1. Field of the Invention
The present invention relates to the art of bookbinding and, particularly, to the completion of manufacture of a book by the application of case, i.e., the interconnected front and back covers and the spine, to an inner book, i.e., the body of the book. More specifically, this invention is directed to improvements in the "casing-in" phase of book production and, especially, to reliably forming an adhesive bond between the articulation regions, i.e., the hinge areas, defined by folds in a book cover and the underlying shaped areas of an inner book which function as hinges, i.e., the areas in which bending of the pages occurs when the book is read. Accordingly, the general objects of the present invention are to provide novel and improved methods of such character.
2. Description of the Prior Art
In the industrial production of books, i.e., in bookbinding procedures performed on a commercial scale, the final manufacturing steps which are performed are incident to the application of a case to the finish-machined inner book. As is well known, in the binding of a hard cover book, a body of leaves, forming the inner book, is joined to the case. The case includes a pair of cover boards and a spine, the spine being located intermediate the cover boards and spaced therefrom. The cover boards and spine are interconnected by, and bonded to, a sheet of flexible covering material, typically, paper. The hinge areas of the case are defined by folds, i.e., creases, which are formed in the flexible covering material intermediate the facing edges of the spine and the cover boards. The step of mating a case with an inner book is known in the art as "casing-in". The "casing-in" procedure is customarily followed by an operation known as "burning-in of the folds" in which the hinge areas of the case are formed. The "burning-in" operation may be coupled with the step of "pressing of the book as a whole".
An example of a prior art "casing-in" process and machine is described in published German Patent Specification 14 36 086. In the process practiced with this prior art apparatus, inner books, standing on the front "cut" thereof, are delivered to the casing-in station where they are individually engaged by saddle plates of a vertical conveyor. The thus engaged inner books are transported upwardly past oppositely disposed glue application rollers. These rollers deposit an adhesive over substantially the entire outer surface of the end papers or flyleaves of the inner book. A case, extracted from a supply stack, is delivered to a shaping station in which the spine of the case is given its requisite rounded shape through the action of a shaping rail and cooperating folding rails. The case with its shaped back is then moved into the path of movement of an inner book so that the rounded spine portion of the inner book will engage the complementary shaped rounded back portion of the case. The thus mated case and inner book then passes between pressure rollers which ensure the establishment of intimate contact between the insides of the cover, i.e., the cover boards, and the adhesively coated end papers. The "cased-in" book is then discharged from the vertical conveyor and delivered to a "burning-in station".
An example of a prior art "burning-in" process and apparatus is disclosed in U.S. Pat. No. 2,921,322, the "burning-in" apparatus being shown as combined with a "casing-in" apparatus to form a final assembly-line stage of a bookbinding operation. The "burning-in" apparatus of U.S. Pat. No. 2,921,322 is defined by a multiplicity of pressing devices which are disposed in a straight row with uniform mutual intervals therebetween. Each of the pressing devices includes a pair of pressure plates which are located opposite to one another with a variable interval. These plates apply compressive force to the sides of an engaged book. Heated rails for "burning-in" the folds, i.e., for producing the articulation areas of the case, are associated with the pressing devices. These heated rails operate in pairs to shape the book case folds. The rails are located on a carriage and, simultaneously with forming the folds, serve as a transport mechanism to move the books stepwise from pressing station to pressing station.
The "burning-in" of the folds, as accomplished employing apparatus of the type disclosed in U.S. Pat. No. 2,921,322, produces a recessed, generally triangular region in the covering material of the case along the facing inner edges of each of the two oppositely disposed cover boards. These recessed regions or "folds", as noted above, are formed by the application of heat and pressure. In order to ensure that the folds will retain their shapes once formed, the covering material in the fold regions should be adhesively bonded to underlying hinge joint regions of the inner book. In order to accomplish this required adhesive bonding, it has been previous practice to deposit a glue dispersion in the hinge joint regions of the inner book prior to performance of the casing-in procedure.
The heated rails which "burn-in" the folds in the cover have had the dual function of plasticizing the covering material of the cover, whereby the covering material is permanently deformed and residual tensile stresses which would tend to restore the flexible covering material of the case to its original shape are reduced, and heating the glue dispersion which has been applied in the hinge joint regions of the inner book to "activate" the adhesive. The formation of the adhesive bonds in the hinge areas should preferably be accomplished in such a manner that the book can be transported immediately subsequent to its release from the book-pressing/burning-in station without danger of the adhesive bonds being broken.
The adhesive bonding of the fold regions of the covering material of the book cover to the inner book, in accordance with the prior art, occurs in phases. Firstly, the uncoated fold regions in the covering material are wetted by the glue dispersion which has previously been applied in the joint regions of the inner book. This wetting results from the pressing of the covering material of the book case against the inner book by the heated rails which perform the "burning-in". Secondly, heat transferred from the rails will cause setting of the glue by driving off the solvent of the dispersion, typically water. During this heat transfer phase, the viscosity of the glue, and the cohesion in the film of glue as well as its adhesion to the surfaces with which it is in contact, will increase. Also, the water or other solvent which is extracted by the heat will penetrate the surrounding paper fibers, this penetration being accelerated by heat transfer from the fold forming rails during "burning-in". However, a relatively long time is nevertheless required before there is sufficient adhesion between the covering material and inner book to prevent detachment of the covering material from the inner book as a result of remaining tensile stresses and/or forces applied during subsequent book transport.
In an effort to overcome the above-briefly discussed problem, and as exemplified by the teachings of U.S. Pat. No. 2,921,322, it has previously been thought necessary that the book-pressing and burning-in of the book case hinge area defining folds be accomplished in step-wise fashion.
The disclosures of the above-referenced publications are hereby incorporated herein by reference.